The present invention relates to a marine vessel propeller comprising an even number of blades such as 4, 6, 8, which can be mounted or demounted to a hub made of two parts each having the half of the blades. The blades can be rigidly connected to each other by means of connecting members.
Propulsion required for the movement of marine vessels sailing afloat such as boats, ships and under water such as submarines is provided by propellers. Propellers, in general, consist of a central hub and plurality of blades combined with the hub. The surfaces of the propeller blades are generally helicoidal and the flowing water is caught by the leading edge of the blade and compressed on the helicoidal surface to form a pressure and then it accelerates over the blade and leaves from the trailing edge. The course of the fluid on blade surface, and hence the water compression on blade surface affect the amount of thrust to be obtained.
Propellers are conventionally cast in one piece and produced after being machined. In other words, the blades are integrally produced with the hub. This structure has some disadvantages: For example, blades, in general, are not allowed to overlap for the removal of the propellers from the cast mold, and for the surface machining after molding; and therefore such blades can get slightly higher than surface area ratio 1:1, generally being under value of 1 (e.g. 0.950). Another disadvantage of the known propellers is that in case one of the blades is damaged due to mechanical fatigue, external impacts, or some other reasons, the entire propeller needs to be replaced. Moreover, in order to obtain a maximum thrust from the blades which are radially aligned around the hub, the blades need to be provided all through the hub thickness (in other words in the direction of hub depth). Manufacturing cost of such a structure of a complicated geometry increases, because it requires a detailed planning during and before the operation; huge counter and machine tracks are needed so as to cover the size of whole propeller.
In order to overcome the abovementioned drawbacks, propellers having demountable blades have been introduced. Such propellers are known to have some certain disadvantages such as having non-uniformly shaped blades. For example, each blade is likely to have different mass from one another when they are produced by casting which is widely-used in blade production. This would inevitably lead to a decrease in thrust performance of the propeller. In fact, the material discontinuity that may occur inside the blade material during casting of the blade or the fact that the blade form cannot be always obtained in its same perfectness cause a balance problem in the propeller. On the other hand, the connection of each blade to the hub may not be of the desired rigidity. For example, the blade-hub connection loses its rigidity because of the vibrations emerging in time, and therefore the blade-to-hub connection weakens and the propeller balance is negatively affected, as a result of which the thrust performance decreases.